The present invention relates to the art of thermal activation optical switches. More particularly, the present invention relates to efficient thermal activation optical switches and the method of fabricating the same.
In the field of electronic and data communications, bandwidth demand is surging because of the rapidly increasing number of users, higher communications access speeds, longer connection times, and the use of rich media, such as audio, video, and high-resolution graphics. Optical networks, having greater bandwidth than traditional electrical networks, are becoming increasingly popular.
For switching optical signals (lights), optical switches based on liquid and bubble technique have been used. In these switches, multiple optical paths are placed in as a matrix on planar-light wave circuits (PLC), or wave-guides, crossing at several intersections, each intersection being a switch. At an intersection, the light travels through fluid with the same optical properties as the wave-guide. As a result, the light travels unimpeded through the intersection.
When the light needs to be rerouted to a new path, a bubble is created in the intersection. The bubble displaces the fluid and alters the optical properties of the intersection, causing the light to be reflected to the new path. The bubble is created by heating the fluid at the intersection and eliminated by removing the heat. The bubble can be generated and removed quickly providing a fast and reliable switching function. For example, the bubble can be generated in several microseconds. Further, the bubble can be sustained by maintaining the heat at the intersection. In fact, by maintaining the heat at the intersection, the switching of the light can be maintained for an indefinite period of time. The heat is typically provided by applying electrical current, or power, through a heating element, usually a high-resistance resistor. The heat is maintained by continuous application of the power through the heating element.
During the generation and the maintenance of the bubble, the heat dissipates to the surrounding material (especially to the substrate on which the heater is fabricated) and is lost. The heat dissipation and loss lead to several problems. First, the switch is inefficient. That is, much of the applied power is lost to the substrate instead of being used to heat the fluid. Second, the power required to generate and to maintain the bubble is greater than the power required to do so without the heat loss. Because of the heat loss, the switch in general and the heater in particular, has a relatively high power requirement. The high power requirement not only increases power costs, but it also increases component costs throughout the entire system. This is because the requirement necessitates the use of components that are able to handle the relative higher power.
Third, the dissipated heat adversely affects surrounding circuits. Fourthly, the heater has a relatively high power density because of the high power requirement. This leads to premature heater problems such as fusing. Fifthly, the high power, thus the current, requirement may required special high voltage high current on-chip circuit which is difficult to do. Finally, because the heat loss, the switch-on time is longer than the switch-on time without the heat loss.
Accordingly, there is a need for an optical switch that overcomes the problems discussed above.
The need is met by the present invention. According to one aspect of the present invention, an optical switch has an insulator on a substrate. A heater is fabricated above the insulator of the substrate, and an optical intersection is constructed above the heater.
According to another aspect of the present invention, a method of fabricating an optical switch is disclosed. First, an insulator is fabricated. Then, a heater is fabricated above the insulator. Finally, an optical intersection is constructed above the heater.
Other aspects and advantages of the present invention will become apparent from the following detailed description, taken in combination with the accompanying drawings, illustrating by way of example the principles of the invention.